linux-kernel - Re: [PATCH 3/3] arm64: reduce trampoline data alignment

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 21 Mar 2020 13:41:01 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Rémi Denis-Courmont <remi@...lab.net>
Cc:     will@...nel.org, linux-arm-kernel@...ts.infradead.org,
        mark.rutland@....com, james.morse@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] arm64: reduce trampoline data alignment

On Thu, Mar 19, 2020 at 11:14:07AM +0200, Rémi Denis-Courmont wrote:
> diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
> index c36733d8cd75..ecad15443655 100644
> --- a/arch/arm64/kernel/entry.S
> +++ b/arch/arm64/kernel/entry.S
> @@ -858,7 +858,7 @@ SYM_CODE_END(tramp_exit_compat)
>  	.popsection				// .entry.tramp.text
>  #ifdef CONFIG_RANDOMIZE_BASE
>  	.pushsection ".rodata", "a"
> -	.align PAGE_SHIFT
> +	.align	4	// all .rodata must be in a single fixmap page
>  SYM_DATA_START(__entry_tramp_data_start)
>  	.quad	vectors
>  SYM_DATA_END(__entry_tramp_data_start)
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 9b08f7c7e6f0..6a0e75f48e7b 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -599,9 +599,8 @@ static int __init map_entry_trampoline(void)
>  	if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
>  		extern char __entry_tramp_data_start[];
>  
> -		__set_fixmap(FIX_ENTRY_TRAMP_DATA,
> -			     __pa_symbol(__entry_tramp_data_start),
> -			     PAGE_KERNEL_RO);
> +		pa_start = __pa_symbol(__entry_tramp_data_start) & PAGE_MASK;
> +		__set_fixmap(FIX_ENTRY_TRAMP_DATA, pa_start, PAGE_KERNEL_RO);
>  	}
>  
>  	return 0;

For some reason, I haven't investigated yet, a kernel with KASAN and 64K
pages enabled does not boot (see the attached config). It seems to lock
up when starting user space. Bisected to this commit, reverting it fixes
the issue.

-- 
Catalin

View attachment ".config" of type "text/plain" (209610 bytes)